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London & South Western class H15
Great Britain | 1914 | 26 produced
Hawkesworth collection

When the London and South Western Railway urgently needed locomotives for heavy freight trains, chief engineer Robert Urie designed the H15 class as a 4-6-0 locomotive with six feet diameter coupled wheels. The same axle configuration and wheel diameter had been used on the F13 in 1905, but the H13 only had two large cylinders on the outside. By also arranging the valve gear on the outside, easy access to all important parts was achieved, which is advantageous for freight locomotives. While Urie was a proponent of superheated steam technology, he was unsure of the best superheater design. For this reason he decided to build different versions of the locomotive.

The first series consisted of four units with Schmidt-type superheaters, four with Robinson-type superheaters and two without any superheaters for comparison. As neither design fully met Urie's expectations, he developed his own superheater and named it the “Eastleigh Superheater” after the factory that built the locomotives. The first locomotive to receive this was converted from the unsuccessful E14 class one-off. Ultimately, the first ten pieces were retrofitted with these superheaters. After the grouping, 15 more examples were built on the Southern Railway under Richard Maunsell. Five of these were created as conversions from the F13 class locomotives.

Schematic drawing with dimensions
Schematic drawing with dimensions
Locomotive Magazine, December 1913

In addition to easy maintenance, good performance and very little wear were also evident in operation. Only the examples converted from the F13 had a very high cab, which presented particular challenges for personnel under six feet tall and earned these locomotives the nickname “Cathedrals”. The originally green and ornate color scheme was changed to a plain black from 1939 under Bulleid. When British Railways was founded, they were classified in the 4P5F power class, i.e. power class four in passenger service and power class five in freight service. The decommissioning of the H15 was completed in 1961, so not a single one was preserved.

VariantsaturatedRobinson superheaterSchmidt superheaterEastleigh superheater
Built19141914, 1924-1925
Axle config4-6-0 (Ten-wheeler) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length65 ft 6 3/4 in
Wheelbase26 ft 7 1/2 in
Fixed wheelbase13 ft 9 in
Total wheelbase57 ft 1 1/2 in
Service weight174,160 lbs177,184 lbs174,384 lbs
Adhesive weight130,032 lbs131,264 lbs130,032 lbs
Total weight302,960 lbs305,984 lbs303,184 lbs
Water capacity6,005 us gal
Fuel capacity11,200 lbs (coal)
Power sourcesteam
Estimated power900 hp (671 kW)1,200 hp (895 kW)1,300 hp (969 kW)
Optimal speed22 mph29 mph32 mph
Starting effort26,239 lbf25,511 lbf
Power Plant
Driver diameter72 in
Boiler pressure180 psi175 psi
Expansion typesimple
Cylinderstwo, 21 x 28 in
Grate area30 sq ft31.5 sq ft
Firebox area167 sq ft168 sq ft
Tube heating area2,025 sq ft1,716 sq ft1,759 sq ft1,716 sq ft
Evaporative heating area2,192 sq ft1,883 sq ft1,926 sq ft1,884 sq ft
Superheater area371 sq ft394 sq ft308 sq ft
Total heating area2,192 sq ft2,254 sq ft2,320 sq ft2,192 sq ft
Calculated Values
steam locomotive
Robert Wallace Urie
last changed: 02/2022

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